Formulation of Two Nodes Finite Element Model for Geometric Nonlinear Analysis of RHS Beams Accounting for Distortion and Shear Deformations

Meftah Sid Ahmed,Abdelouahed Tounsi,Pham Van Vinh 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.4

In this paper, the nonlinear buckling analysis of rectangular hollow sections (RHS) beams considering distortional and the shear fl exibility deformation eff ects is investigated. The kinematic model is based on the incorporation of non-classical terms, related to shear fl exibility, according to Timoshenko model and distortion and warping. This analysis is carried out by proposing a new 3D fi nite element, formulated in the context of large torsion, incorporating fl exural torsion, and distortion coupling eff ects. A 3D RHS beam element with two nodes and eleven degrees of freedom per node is proposed to perform the nonlinear buckling analysis. For this aim, the arc-length method is employed as a solution strategy to solve the nonlinear equilibrium equations, established as a function of the trigonometric functions of the twist angle. Many examples are proposed to check the validity of the proposed 3D fi nite element and the numerical procedure, either in pre-and postbuckling states. The present numerical results are compared to those of the commercial software ABAQUS using the brick fi nite elements. The incidences of the compressive load and the incorporated lateral stiff eners in the RHS beams in pre- and post-buckling behaviour are studied.

Web Applications Development by Formal Refinement Approach

Meftah Mohammed Charaf Eddine,Kazar Okba 보안공학연구지원센터 2015 International Journal of Software Engineering and Vol.9 No.12

This paper proposes a formal approach for development of safe web applications. This approach involves the generation of a web application on both sides (users’ side (Ajax) and the web service side (Composition)) from formal specifications. First, we describe the application using symbolic notations then an automatic process is applied in order to translate them into formal specifications B. Using the B refinement process, a set of refinement rules, operating on data and operations. These phases of refinement are intended to make the final specifications close to the implementation language chosen so that the last coding phase becomes intuitive and natural. In general, the process of refinement is a manual task, relatively expensive; with character generic of these refinement rules, an assisted refinement tool can be achieved, enabling reduction the cost of the refining process. Finally, in the case study, we have developed a complete application (Travel Agency) in order to show the benefits of our approach.

A non-polynomial four variable refined plate theory for free vibration of functionally graded thick rectangular plates on elastic foundation

Ali Meftah,Ahmed Bakora,Fatima Zohra Zaoui,Abdelouahed Tounsi,El Abbes Adda Bedia 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.3

This paper presents a free vibration analysis of plates made of functionally graded materials and resting on twolayer elastic foundations by proposing a non-polynomial four variable refined plate theory. Undetermined integral terms are introduced in the proposed displacement field and unlike the conventional higher shear deformation theory (HSDT), the present one contains only four unknowns. Equations of motion are derived via the Hamilton's principles and solved using Navier's procedure. Accuracy of the present theory is demonstrated by comparing the results of numerical examples with the ones available in literature.

Milne type inequalities for differentiable $s$-convex functions

Badreddine Meftah,Meriem Djenaoui 호남수학회 2022 호남수학학술지 Vol.44 No.3

In this paper, a new identity is given. On the basis of this identity, we establish some new estimates of Milne's quadraure rule, for functions whose first derivative is $s$-convex. We discuss the cases where the derivatives are bounded as well as Lipschitzian. Some illustrative applications are given.

Seismic Behavior of RC Coupled Shear Walls with Strengthened Coupling Beams by Bonded Thin Composite Plates

S. A. Meftah,F. Mohri,E. M. Daya 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.2

The present study investigates the dynamic analysis of Reinforced Concrete (RC) coupled shear walls strengthened by bonded Carbon Fibre Reinforced Polymer (CFRP) composite plates applied on both sides of the coupling beams. For this purpose, new finite element models are developed for both the walls and strengthened coupling beams. In the validation process of the proposed model,static and free vibration analyses of coupled shear walls were firstly studied. Comparisons with ABAQUS code using shell elements were made and good agreement was observed. After this stage, dynamic analysis was carried out under El Centro and Northridge earthquake records. In these conceptual studies, the maximum top lateral deflection responses of strengthened and unstrengthened RC coupled shear walls are computed. The obtained results showed that mitigation of seismic behaviour of RC coupled shear walls by using CFRP bonded composite plates depends on the geometrical characteristics of shear wall structure and dominant range frequencies of the input earthquake records.

Dynamic behaviour of stiffened and damaged coupled shear walls

S. A. Meftah,A. Tounsi,E. A. Adda-Bedia 한국계산역학회 2006 Computers and Concrete, An International Journal Vol.3 No.5

The free vibration of stiffened and damaged coupled shear walls is investigated using the mixed finite element method. The anisotropic damage model is adopted to describe the damage extent of the reinforced concrete shear wall element. The internal energy of a locally damaged shear wall element is derived. Polynomial shape functions established by Kwan are used to present the component of displacements vector on each point within the wall element. The principle of virtual work is employed to deduce the stiffness matrix of a damaged shear wall element. The stiffened system is reinforced by an additional stiffening beam at some level of the structure. This induces additional axial forces, and thus reduces the bending moments in the walls and the lateral deflection, and increases the natural frequencies. The effects of the damage extent and the stiffening beam on the free vibration characteristics of the structure are studied. The optimal location of the stiffening beam for increasing as far as possible the first natural frequency of vibration is presented.

Performance Study of the Micromorph Silicon Tandem Solar Cell Using Silvaco TCAD Simulator

A. F. Bouhdjar,M. Adaika,Am. Meftah,R. Boumaraf,Af. Meftah,N. Sengouga 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.6

This paper is concerned with the numerical modelling of a micromorph silicon tandem solar cell (a-Si:H/μc-Si:H), under series (two-terminal: 2T) and independent (four-terminal: 4T) electrical connection. The study is performed using the simulation software Silvaco TCAD. Both the initial (un-degraded or annealed) state, and the light induced degradation one (wellknown Staebler–Wronski effect in a-Si:H) are considered for the studied solar cell, operating under the standard global solar spectrum (AM1.5G). The 2T- and 4T-device optimization is carried out under the eff ects of the intrinsic (i)-layer thickness ofthe two sub-cells, and the free carrier mobilities through these layers. By increasing the i-layer thickness of the two sub-cells, the 2T-micromorph tandem cell reveals an optimal conversion efficiency n of 10% and 7.77% corresponding, respectively, to the initial and degraded states. The 4T-configuration exhibits a relatively better n of 10.94% at initial state, reduced only to 9.59% at the degraded one. Further improvement of the 2T and 4T-cell output parameters is obtained by increasing the free carrier mobilities, particularly through the top-cell i-layer. By this way, the better n is also ensured by the 4T-device, which displays an initial state-n of 12.31%, reduced only to 11.43% at the degraded state. However, the improved effi ciencies reached by the 2T-confi guration are 11.87% and 10.41% corresponding, respectively, to the initial and degraded states.

Investigation of the Instability of FGM box beams

Ziane, Noureddine,Meftah, Sid Ahmed,Ruta, Giuseppe,Tounsi, Abdelouahed,Adda Bedia, El Abbas Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

A general geometrically non-linear model for lateral-torsional buckling of thick and thin-walled FGM box beams is presented. In this model primary and secondary torsional warping and shear effects are taken into account. The coupled equilibrium equations obtained from Galerkin's method are derived and the corresponding tangent matrix is used to compute the critical moments. General expression is derived for the lateral-torsional buckling load of unshearable FGM beams. The results are validated by comparison with a 3D finite element simulation using the code ABAQUS. The influences of the geometrical characteristics and the shear effects on the buckling loads are demonstrated through several case studies.

Investigation of the Instability of FGM box beams

Noureddine Ziane,Sid Ahmed Meftah,Giuseppe Ruta,Abdelouahed Tounsi,El Abbas Adda Bedia 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.3

A general geometrically non-linear model for lateral-torsional buckling of thick and thin-walled FGM box beams is presented. In this model primary and secondary torsional warping and shear effects are taken into account. The coupled equilibrium equations obtained from Galerkin's method are derived and the corresponding tangent matrix is used to compute the critical moments. General expression is derived for the lateral-torsional buckling load of unshearable FGM beams. The results are validated by comparison with a 3D finite element simulation using the code ABAQUS. The influences of the geometrical characteristics and the shear effects on the buckling loads are demonstrated through several case studies.

Eff ect of Shear and Distortion Deformations on Lateral Buckling Resistance of Box Elements in the Framework of Eurocode 3

Abdelkader Saoula,Sid Ahmed Meftah 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.4

This paper treats the distortional and shear deformation eff ects on the elastic lateral torsional buckling of thin-walled box beam elements, under combined bending and axial forces. For the purpose, a nonlinear kinematic model based on higher order theory is used applicable to both short and long thin-walled box beams. Because in the kinematic model of the higher order theory integrates additional fl exibility terms related to shear, distortion and warping eff ects, it accurately predicts the lateral torsional buckling of the straight box beams. Ritz’s method is adopted as solution strategy in order to obtain the nonlinear governing equilibrium equations, then the buckling loads are computed by solving the eigenvalue problem basing on the singularity of the tangential stiff ness matrix. Owing to fl exural–torsional and distortional couplings, new matrices are obtained in both geometric and initial stress parts of the tangent stiff ness matrix. The proposed method with the new stiff ness terms, is effi cient and accurate in lateral torsional buckling predictions, when compared with the commercial FEM code ABAQUS results. Based on the existing European guidelines EC3, an extensive numerical investigation is performed to demonstrate the eff ects of both shear and distortional deformations on the moment carrying capacity. The convenience of the model is outlined and the limit of models developed without shear and distortion deformation eff ects on lateral buckling loads evaluation is discussed.